From: "Amir G." Subject: Re: Introducing Next3 - built-in snapshots support for Ext3 Date: Fri, 7 May 2010 21:22:56 +0200 Message-ID: References: <20100504224226.GE6344@thunk.org> <87vdaz21b0.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: tytso@mit.edu, linux-ext4@vger.kernel.org To: Andi Kleen Return-path: Received: from mail-bw0-f219.google.com ([209.85.218.219]:46796 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755971Ab0EGTW6 (ORCPT ); Fri, 7 May 2010 15:22:58 -0400 Received: by bwz19 with SMTP id 19so769782bwz.21 for ; Fri, 07 May 2010 12:22:56 -0700 (PDT) In-Reply-To: <87vdaz21b0.fsf@basil.nowhere.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, May 7, 2010 at 5:12 PM, Andi Kleen wrote: > "Amir G." writes: >> >> Yes, of course, I realize that. This is the reason I chose to >> introduce Next3 as a new f/s, >> which was branched from Ext3 and not as a new feature to Ext3. >> Unfortunately, merging Next3 snapshots feature into Ext4 is not an easy task, >> because extent mapped files break the design concepts of Next3 snapshots. > > As I understand it the ext4 code base still supports not having > extents enabled in the super block (although I'm not sure how well > that variant is tested in practice) > > So in theory you could have a feature that requires disabling extents. > > It might not make users very happy though. > In theory, it is possible to have 2 modes for Ext4 (extents or snapshots) and some would argue that it makes sense to do that. But I think that making that decision can be deferred to a later time, after people have experienced with Next3 and have decided if they would like to have the snapshot feature merged into Ext4 or not. Besides, it would take me a considerable amount of time to merge the snapshot feature into Ext4, and Next3 is ready to be used now. Amir.